View Full Version : Cold Cathode light and Variable contrast paper

Colin Myers
17-Nov-2005, 06:56
Does anyone have direct experience of using single tube, cold cathode lights sources and variable contrast paper. I have read somewhere that it is possible to use additional, below lens filters, to simulate the green tube(soft grade) effect. Any thoughts on this ? I would be most grateful for any input
Colin Myers

Mark Sampson
17-Nov-2005, 07:30
I've used variable-contrast papers and a (blue) Zone VI stabilized cold-light for many years. I put Kodak filters beneath the lens to control contrast. My "normal" filter with this setup is the #1. With a tungsten light source the same neg prints with a #2 filter. Some people suggest a CP40Y filter above the neg to correct the lamp color, but I find this unnecessary; I feel it just adds neutral density and so slows things down. I have no problem reaching very high or low levels of contrast, but I do try to make negs that don't need extremes of paper contrast. I've occaisionally found that a 1/2 grade filter change gives more contrast change in the print than I want, but that's rare, and I've been able to work around it. A new tube with the correct phosphor for VC paper sounds good, but I haven't tried it yet.

ronald lamarsh
17-Nov-2005, 07:38
I have been using a V54 aristo cold lamp for a number of years now and have a tungsten diffusion enlarger also. I use below the lens filters(kodak polymax) and have done a number of comparsion tests between the 2 enlargers. I have also had the opportunity to use a newer enlarger at a workshop with a dicro head. To the best of my a bility i have not been able to tell any difference between any of them i.e. contrast range of papers etc. If you have a "blue light only" light source get Steve Anchells book on variable contrast printing it has very good information on how to get a blue light only unit to work. As an aside in Anchells book he compares several different papers,filter systems and 2 different light sources. It is very enlightening as it shows little to no difference in contrast ranges of papers when using different light sources or filter systems, the biggest differences are in the paper's themselves.

Neil Miller
17-Nov-2005, 09:39
Hello Colin,

I have used a DeVere cold-cathode with below the lens filters for five years or so (just got a dichro head, though). The output from the DeVere cc head has quite a strong blue colour.

I found that half-step increments in contrast were a bit problematical (same as Mark points out), but it worked very well indeed with whole steps, except at either end of the scale where changes were very hard to discern.

However, for grades 2 to 5 steps were predictable and worked well (without any filtration at all my setup gave me the equivalent of about 2.5).


John Berry ( Roadkill )
17-Nov-2005, 10:47
I read that a light green filter under light source is used to change color output so that filters will act more like they would with a tungston source.

Donald Qualls
17-Nov-2005, 11:32
I've got a Zone VI cold light -- can't say for certain it's cold-cathode, but I suspect all of them are (instant start instead of the flicker-flicker-blink-start of a common fluorescent), and I don't know for certain if it's a "blue" or a VC type; the light looks bluish-white to my eye, similar to the color of a "white" LED. I've been very happy with my results split filtering under it using Lee theatrical lighting filters, Dark Blue 119 and Spring Yellow 100 for hard and soft respectively. I get contrast grades I estimate as ranging from 1 to 6; I may shop for a yellow or green with 20-50 nm longer cutoff wavelength to see if I can soften the soft end a little more.

FWIW, on what I'm used to considering a "normal" negative, I wind up using approximately equal exposure times with the two filters...

Colin Myers
18-Nov-2005, 00:43
Thanks everyone for your input on this, most helpful